Device for thermal ablation of a cavity

ABSTRACT

An apparatus and method for causing necrosis of tissue and specifically intended for thermal ablation of the uterine cavity to cauterizing the endometrial tissue. The apparatus includes a liquid-tight, liquid filled system having a distal flexible member; a proximal flexible member; and a catheter joining and providing a liquid path between these distal and proximal members. The apparatus further includes a pressurizable pneumatic chamber into which the proximal flexible member is inserted and a means to controllably heat the contents of the pneumatic chamber. The system operates to: first withdraw substantially all of the liquid into the proximal flexible member contained within the pressurizable pneumatic chamber; second to heat this liquid to a temperature such that it can cause tissue necrosis; and third to force the heated liquid from the proximal flexible member into the distal flexible member where it is maintained for a predetermined time and at a predetermined pressure. Where this distal member has been inserted into a uterine cavity or is otherwise is in contact with living tissue, the presence of the heated liquid results in tissue necrosis and cauterization.

TECHNICAL FIELD

[0001] The disclosed invention relates to an apparatus or device foreffecting hyperthermia in a body cavity or duct. More specifically, theinvention relates to apparatus and methods using a balloon or similarflexible bladder which is inserted into the uterus and filled with aheated liquid at a known pressure and for a known time in order tocauterize (“ablate”) the endometrium of the uterus. This method oftreatment is known as “thermal balloon ablation”.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] Medical treatments involving ablation of the endometrium of theuterus are well known in the prior art. The endometrium is the portionof the uterine lining to which an embryo normally attaches and isresponsible for the menstrual cycles. Such ablation treatments typicallyinvolve either the direct or indirect application of heat or cold to theendometrial tissue. Commonly, ablation devices and techniques have beenused to treat menorrhagia (a condition of excessive menstrual bleeding)by cauterizing, or inducing necrosis of the endometrial lining. Thiscauterization prevents further proliferation of the endometrium and mayresult in permanent relief of menorrhagia symptoms.

[0003] Apparatuses for thermal balloon ablation are well known in theprior art. For applications to treat the endometrium of the uterus,thermal balloon ablation apparatuses typically comprise a distensibleballoon which is inserted into the uterus through the external openingof the cervix. The balloon is then inflated with a liquid to expand theballoon such that it is in contact with substantially all of the uterinecavity. This liquid is then heated to a controlled temperature by aheating element within the balloon and the liquid is maintained at thistemperature for a predetermined period of time. After this period oftime has elapsed, the liquid is withdrawn and the balloon removed fromthe uterus. The heat energy which is transferred from the liquid filledballoon to the surrounding tissues of the uterus causes the desiredcauterization of the endometrium. There are many examples of suchdevices in the prior art, for example those disclosed by Stevens etal—U.S. Pat. No. 5,800,493, and Wallsten et al—U.S. Pat. No. 5,693,080 &U.S. Pat. No. 5,571,153.

[0004] Typically the volume of liquid required to inflate the balloonranges between 5 ml and 30 ml and is dependent on the natural volume ofthe uterine cavity and the liquid pressure. According to studiespublished in the medical literature, the liquid pressure should notexceed 180 mmHg applied to the uterine cavity walls above which there isrisk of mechanical damage to the deeper tissue of the uterus.

[0005] Variations on thermal balloon apparatuses and methodologiesinclude cryogenic apparatuses which use cooled liquid rather than heatedliquid to achieve necrosis of the tissue (such as that disclosed byLafontaine et al—U.S. Pat. No. 5,868,735) and apparatuses in whichheated liquid is circulated through the uterus without the benefit of aflexible balloon to contain the liquid (such as that disclosed byGoldrath—U.S. Pat. No. 5,437,629).

[0006] A variety of alternatives to thermal balloon ablation are knownfor cauterization of endometrial tissue. These includes the use ofmicrowave, RF, laser, electrical current or similar energy sources toheat a surgical probe inserted through the cervix and which ismanipulated by means of direct hysteroscopic visualization. Thesedevices typically require a highly skilled operator and producetreatment results which are more variable than those which can beachieved through thermal balloon ablation techniques. Such alternativeablation techniques also pose higher risk of perforating the uterus,normally require use of general anesthesia, and have a higher incidenceof post-operative complications than thermal balloon ablationtechniques.

[0007] In spite of the potential advantages of thermal balloon ablationtechniques over alternative treatment methodologies, problems with thethermal balloon ablation apparatuses in the prior art have preventedsuch devices from being adopted widely for use in the treatment ofmenorrhagia.

[0008] Thermal balloon ablation systems in the prior art typically relyon heating elements located within the balloon. During heating, thesedevices often develop temperature gradients in the liquid which canresult in uneven treatment of the endometrial surface. Typically theobserved effect is to over-treat the area of the endometrium directlyabove the heating element and under-treat the area of the endometriumlocated directly below. This effect is magnified if the heating elementwithin the balloon is inserted at an angle relative to theanterior/posterior plane of the uterus such that after inflation theheating element is located closer to the anterior wall of the balloon.Placement of the heating element relative to the balloon walls isdifficult to control in practice. To reduce this problem, someinventions in the prior art include provision of an impeller,reciprocating piston or similar mechanical means to stir the liquidduring heating (such as those disclosed by Neuwirth et al—U.S. Pat. No.5,460,628 and Saadat et al U.S. Pat. No. 5,827,269) or utilize balloonswhich allow injection and re-circulation of heated liquid via multiplelumens, typically an “intake” lumen and an “exhaust” lumen (such as thatdisclosed by Lafontaine et al—U.S. Pat. No. 5,868,735). Furthermore,pulsing the liquid pressure is an alternative means to achieve moreuniform mixing of the liquid (as described by Wallsten et al U.S. Pat.No. 5,957,962). However, such circulating methodologies add cost andcomplexity to the apparatus and the ability to achieve desiredtemperature uniformity depends among other factors on the volume ofliquid within the balloon.

[0009] Thermal balloon ablation devices in the prior art such as thatdisclosed by Stevens et al—U.S. Pat. No. 5,800,493 have also relied onthe operator to provide the liquid for inflation of the balloon andheating. This has limited the variety of liquids to those typicallyfound in a clinical environment (e.g. D5% W or saline). Such liquids aregenerally water based and therefore cannot be heated above approximately100C, at which temperature these solutions begin to boil at sea level.Heating liquid to the boiling point can result in a dangerous increasein balloon volume due to expansion of gas and in uneven treatment sincethe presence of this gas pockets in the balloon act to thermallyinsulate the adjacent tissue. The maximum temperature limitation ofthese liquids has resulted in relatively long treatment times; it iswell established in the research and in clinical practice that itrequires in approximately 8 minutes to cauterize the endometrium bythermal balloon ablation using liquid temperatures of 85C. Furthermore,the use of liquid temperatures in the range of 70-90C makes the use ofliquid heating means external to the uterus or balloon ineffective sincein this temperature range there is insufficient heat energy containedwithin the volume of liquid within the uterus to adequately cauterizethe endometrium. In devices that employ heating means external to theballoon in the uterus and which use liquid temperatures below 100C (suchas that disclosed by Chin U.S. Pat. No. 5,449,380) it is generallynecessary to continuously circulate the liquid between the balloon andthe external heating means in order to maintain an elevated liquidtemperature within the uterus and to achieve the desired treatment. Inaddition, devices with heating elements located in the balloon withinthe uterus prohibit the use high viscosity liquids (such as 100%Glycerin) which resist flow at ambient temperatures but once heatedbecome less viscous and can readily flow through a catheter to inflate aballoon placed in the uterus.

[0010] Systems which require the operator to supply the inflation liquidare also complicated for the operator to use. It is necessary for theoperator to obtain a source of sterile liquid, inject the liquid intothe system, check for leaks, purge gas or excess liquid from the system,and then dispose of the heated liquid after treatment. This process alsocompromises the sterility of the system since there is potential fornon-sterile or contaminated liquid to circulate within the balloon. Inthe event of a balloon leak or rupture, this non-sterile liquid isreleased into the uterine cavity and could result in infection.

[0011] Devices in the prior art typically rely on mechanical actuators,syringes, or liquid pumps which come into contact with the treatmentliquid in order to control inflation and pressurization of the balloon,these can be expensive, unreliable, and subject to contamination. Oftenthese systems require the operator to manually inject liquid to fill theballoon. Furthermore such systems (such as that disclosed by Stevens eta—U.S. Pat. No. 5,800,493) typically have expensive disposablecomponents as these components often include hoses, valves, connectors,electrical wiring, syringes, and heating elements which must be disposedof after each use. Wallsten et al have attempted to address this problemin the invention disclosed in U.S. Pat. No. 5,957,962 in order toprovide an inexpensive disposable component however the described systemstill requires the addition of liquid from an external source, purgingof gas from the system and relies on a mechanical apparatus andactuators to inject and remove liquid from the treatment balloon.

[0012] Often it is difficult for the operator to control inflationpressure and there is not adequate means to control this pressure inresponse to changes in uterine volume during treatment (typically theuterus relaxes and expands as treatment progresses and therefore it isdesirable to increase the volume of liquid in the balloon to maintain aconstant inflation pressure). Wallsten et al U.S. Pat. No. 5,693,080discloses apparatus intended to allow automated control of inflationpressure through mechanical actuation of syringes or similar meanshowever this is costly and does not allow fine control of pressures.Wallsten et al further disclose a means for providing overpressurerelief in the event of a increase in balloon pressure such as that whichmight be caused by a sudden contraction of the uterus during treatmenthowever this does not provide a practical or inexpensive means forautomated control of balloon inflation, deflation, and liquid pressure.

[0013] Prior art devices also rely on the operator to sound the depth ofthe uterus then insert a catheter or treatment element to a depth of nogreater than the previously sounded depth. This requires effort on thepart of the user to measure depth and observe insertion depth as markedon the treatment device. There is a danger of perforating the uterus byover-inserting the catheter if the clinician does not perform thisoperation properly.

[0014] In providing thermal balloon ablation treatment, it is desirousto: provide uniform cauterization of the endometrial tissue; ensure thatany material which can potentially come into contact with the patient issterile; provide the treatment in as short a period of time as possible;deliver the treatment in a manner which does not depend on the skilllevel of the operating clinician; and minimize the cost of anydisposable components associated with the treatment apparatus. It isfurther desirable to avoid cauterization of the cervical canal duringtreatment, and to minimize the risk of perforation of the uterus whenthe balloon is inserted through the cervical opening or during thetreatment period.

[0015] Ideally the device should be simple for the operator to use andshould require minimal preparation for use by the operating clinician.

[0016] Accordingly, the present invention provides an apparatus forcausing necrosis of a body cavity or duct, specifically the uterus, saidapparatus comprising:

[0017] a disposable portion of the apparatus comprising a sealed systemconsisting of a liquid within said sealed system, an elongated distalsection with a flexible balloon (or bladder) attached to it, a proximalflexible balloon (or bladder), and a means for connection to a permanentnon-disposable apparatus;

[0018] a means for heating said liquid; and

[0019] a permanent non-disposable apparatus comprising, a pneumaticpressurizing means for initiating flow of the liquid within said sealedsystem of the disposable portion of the apparatus, connection means forsaid disposable portion to permanent portion, and a controlling meansfor heating, pneumatic pressure, and time.

[0020] An object of the invention is to provide an apparatus whichfurnishes a means for shortened treatment time by incorporating a sealeddisposable component containing a volume of liquid provided by themanufacturer. A liquid filled and sealed disposable apparatus providesone advantage as it allows the use of liquids which are not typicallyencountered in a clinical environment and which can be heated totemperatures in excess of 100C without boiling (for example 100%Glycerin). This allows improved cauterization of the endometrial liningof the uterus and shortens treatment times from 8 minutes at 85C toapproximately 1.5 minutes at 165C. Furthermore, by pre-heating theliquid external to the patient, high viscosity liquids (such as 100%Glycerin) can be used which flow readily at higher treatmenttemperatures. Because of the high viscosity at ambient temperatures,such liquids could not be readily utilized in apparatus where theheating means is located inside the balloon which is inserted into theuterus.

[0021] Another object of the invention is to provide a means of ensuringuniform treatment of the uterine cavity. The apparatus achieves theobjective by injecting a pre-heated, isothermal volume of liquid intothe distal flexible bladder within uterine cavity. Therefore at the timeof injection into the uterus, all areas of the uterus are contacted witha uniform high temperature (approximately 165 degrees Celsius) liquid.

[0022] Another objective of the apparatus is to provide a low cost, easyto use system, that is safe and effective. The described apparatusprovides for improved ease of use and reduced costs by using adisposable component comprising primarily: two flexible enclosuresjoined by a liquid path and containing a liquid; and a fitting whichpermits the proximal flexible enclosure to be sealed inside there-usable pneumatic chamber. By using a sealed system containing a bolusof liquid, the operator simply installs the disposable cartridge andinitiates heating. There is no need to source liquid, fill the system,or purge gas from the system. This makes the apparatus much easier touse and improves patient safety by ensuring sterility of the system.Since the liquid is contained in a sealed system and is driven bypneumatic means, in the event of a balloon rupture only sterile liquidcan be released into the uterus. The disposable component does notinclude valves or fluid pumping means and can therefore be manufacturedfor minimal cost.

[0023] A further object of the invention is to automate ballooninflation and control of balloon inflation pressure. The describedapparatus provides improved control of balloon inflation pressure bymodulating pneumatic pressure within a chamber external to the patient.This pressure can be readily monitored and automatically controlled witha high degree of accuracy to achieve the desired inflation pressure ofthe distal balloon during the treatment period, adapting quickly tochanges in uterine volume due to relaxation or contraction of theassociated musculature. By using pneumatic pressure to transfer liquidfrom the proximal flexible balloon into the distal flexible balloon andwithdraw liquid from the distal flexible balloon, the system achieves ahigh degree of control and reduces user errors.

[0024] Yet another object of the invention is to provide a physicalmeans to indicate when the proper depth of insertion of the balloon isachieved. The described apparatus uses a soft rubber flange (“cervicaltab”) around the insertion catheter which is larger than the cervicalopening. This prevents insertion of the catheter beyond a predetermineddepth into the uterus. The apparatus is configured such that when thecatheter is inserted until this cervical tab rests against the proximalcervical opening, the associated treatment balloon can deploy to treatthe indicated range of uterine sizes and volumes. Before treatment, theoperator confirms by examination that the uterine depth and volume fallwithin this predetermined range, then the operator simply inserts theballoon until the cervical tab rests against the cervix. The operatordoes not need to change the depth of insertion or manner of use fordifferent patients. As a result, there is minimal risk of perforatingthe uterus and treatment methodology is greatly simplified for the user.

[0025] A further object of the invention is to provide a means ofpreventing any treatment to the cervical canal. This is achieved by athermal insulating sheath, which surrounds the liquid delivery catheter.When the treatment balloon and liquid delivery catheter are insertedsuch that the cervical tab rests against the cervix, the insulatingsheath located distal to the cervical tab is precisely positioned withinthe cervical canal. This sheath has thermal insulating capabilities,which limit the heat transfer between the liquid delivery catheter andthe patient's cervix and prevents unwanted treatment of this area.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1a and FIG. 1b provide an overview of the embodiment of theinvention. FIG. 1a shows the reusable and disposable componentsseparately, FIG. 1b shows the invention with the disposable componentinstalled in the reusable component.

[0027]FIG. 2 provides a detailed cross sectional view of the disposablecomponent.

[0028]FIG. 3 shows a detailed cross sectional view of the pneumaticchamber and associated components of the distal end of the reusablecomponent.

[0029]FIG. 4 shows a detailed cross section of the proximal end of thedisposable component and the reusable component when the reusablecomponent is installed such that it is ready for use.

[0030]FIG. 5 provides details of the preferred embodiment of thepneumatic pressurizing means.

[0031]FIG. 6 shows details of the control system contained within thereusable component.

[0032]FIG. 7a shows deployment of the distal end of disposable componentduring treatment of a 7 cm deep uterus which is the smallest indicateduterus for use of the preferred embodiment of the invention.

[0033]FIG. 7b shows deployment of the distal end of disposable componentduring treatment of a 12 cm deep uterus which is the largest indicateduterus for use of the preferred embodiment of the invention.

[0034]FIG. 8 shows an alternate embodiment of the device in which aheating element is contained within the distal balloon.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0035] As shown in the drawings for the purposes of illustration, thepresent invention is embodied in a thermal balloon ablation apparatuswhich comprises a reusable component and a disposable component fordelivering therapy to a body cavity.

[0036] In accordance with the present invention as shown in FIG. 1a andFIG. 1b, the thermal balloon ablation apparatus comprises a reusablecomponent 2 and a disposable component 4. Reusable component 2 furthercomprises a housing 6 which has a handle 8. Integral to housing 6 is adisplay means 10 and user controls 12. Disposable component 4 comprisesa distal balloon 14, a semi-rigid or rigid catheter 16 having a distaland proximal end, a semi-rigid or rigid distal sheath 18, a flange 20, asemi-rigid or rigid proximal sheath 22, a pneumatic fitting 24, aproximal balloon 26, and a protective shield 28.

[0037]FIG. 2 shows a detailed cross sectional view of disposablecomponent 4. Distal balloon 14 can be inflated to volumes of 30 mlwithout generating significant back-pressure and is suitable for use attemperatures in excess of 165C. In the preferred embodiment the balloonis fabricated from 0.12 mm thick silicone rubber, is shaped in theapproximate shape of the uterine cavity and has a natural volume ofapproximately 15 ml, however other materials and shapes are acceptableso long as they allow the balloon to substantially conform to the uteruswhen inflated and provided they facilitate transfer of heat energybetween the liquid contained in the balloon and the endometrium. Distalballoon 14 is bonded in a liquid tight manner to the distal end ofcatheter 16. In the preferred embodiment this bond is made using anadhesive material. The distal end of catheter 16 further includes aplurality of liquid ports 30 located such that they are contained withindistal balloon 14. In the preferred embodiment, proximal balloon 26 isfabricated from silicone rubber and has a natural volume ofapproximately 30 ml. The proximal end of catheter 16 is bonded in aliquid tight manner to the proximal balloon such that a liquid tightsystem exists comprising distal balloon 14, catheter 16 and proximalballoon 26. In the preferred embodiment this bond is made using anadhesive material.

[0038] The liquid tight system comprising distal balloon 14, catheter 16and proximal balloon 26 is filled with liquid 32 such that there existsonly liquid 32 within the system and no significant volume of gas atroom temperature and ambient pressure. Liquid 32 must be non-toxic andpose minimal hazard to the patient in the event that distal balloon 14ruptures. Ideally, liquid 32 should be such that it can be heated totemperatures above 10C without boiling. In the preferred embodiment 100%Glycerin is used which can be heated to temperatures above 165C withoutboiling at ambient pressures. A total volume of approximately 30 ml ofliquid 32 is contained within the system such that the entire volume ofliquid can be contained within the natural volume of the proximalballoon 26 such that distal balloon 14 can be collapsed for insertionthrough the cervix.

[0039] The distal end of catheter 16 further includes an end cap 34fabricated from a soft rubber material in order to reduce the risk ofperforating distal balloon 14 or uterine tissue during insertion intothe uterus. A thermal insulating material 36 is located between catheter16 and distal sheath 18 and between catheter 16 and proximal sheath 22.Thermal insulating material 36 prevents excessive heating of theexternal surfaces of the distal sheath 18 and proximal sheath 22 duringthermal balloon ablation treatment using the apparatus. In the case ofdistal sheath 18, it is desirable to ensure that the temperature of theexternal surface does not exceed 49C in order to prevent necrosis oftissues of the cervical canal, defined as the area between the internalopening (also known as “os”) of the cervix and the external os of thecervix of a patient. In the preferred embodiment, thermal insulatingmaterial 36 is a combination of mica and closed cell silicone rubberfoam. Distal sheath 18 has a diameter of approximately 6 mm such that itcan be easily inserted through the cervical canal of a patient. Distalsheath 18 and proximal sheath 22 are separated by flange 20 which is ofsufficient diameter that it cannot be inserted into the cervical canalof a patient. In the preferred embodiment, flange 20 is fabricated fromsilicone rubber and has a diameter of 12 mm. The dimensions ofdisposable component 4 are intended such that the distal end of theapparatus can be inserted through the cervical opening into the uterusto the point at which flange 20 prevents further insertion, to treatuteri with sounded depths between 7 cm and 12 cm as measured from theexternal cervical opening. Therefore the length of distal sheath 18 plusthe length of catheter 16 protruding distally beyond distal sheath 18 isless than 7 cm. The dimensions of disposable component 4 are alsointended to shield the cervical canal from treatment where the cervicalcanal is defined, for the purpose of this embodiment, as the 3.5 cm longregion immediately internal to the external cervical opening, andtherefore distal sheath 18 is approximately 3.5 cm in length. It will beobvious to one skilled in the art that these dimensions can be varied tosuit the anatomy of the body cavity which is to be treated using theapparatus.

[0040] Proximal balloon 26 is covered by a protective shield 28comprised of a rigid heat conducting material. In the preferredembodiment, this material is thin-walled aluminum with an outer diameterof approximately 2 cm and a length of approximately 10 cm. Any similarmaterial or configuration is acceptable so long as it providesmechanical protection for proximal balloon 26 during handling andinsertion into reusable component 2 and so long as proximal balloon 26makes substantial contact with the inside surface of protective shield28 when the total volume of liquid 32 is substantially contained withinproximal balloon 26. Protective shield 28 is affixed to the proximalside of pneumatic fitting 24. Catheter 16 extends through pneumaticfitting 24 in an airtight manner. Pneumatic fitting 24 further includesa rubber O-ring 38 on its proximal surface.

[0041] It is necessary that all components of the apparatus which maycome into contact with the vaginal canal, cervix or uterus be sterile atthe time of use, non-toxic, and non-allergenic. It is intended thatdisposable component 4 is sterile and will be discarded after each useof the device to treat a single patient.

[0042]FIG. 3 shows a detailed cross sectional view of the pneumaticchamber 40 and associated components of the distal end of reusablecomponent 2. Pneumatic chamber 40 further contains a cylindrical heatingelement 42 and an inner chamber 44. In the preferred embodiment, heatingelement 42 is a 60 watt, electrically powered, flexible membrane typeheater. Inner chamber 44 is cylindrical in shape and approximately 2 cmin diameter and 11 cm in length such that is allows insertion ofprotective shield 28 and the proximal balloon 26 and liquid 32 containedtherein. In the preferred embodiment pneumatic chamber 40 is fabricatedfrom nylon material and inner chamber 44 is fabricated from stainlesssteel. Heating insulation 46 located around the outside of the heatingelement minimizes heat transfer from heating element 42 to the externalsurface of pneumatic chamber 40 and housing 6. A plurality of heatertemperature sensors 48 are located on or adjacent to heating element 42in order to produce a signal indicative of the temperature of heatingelement 42. A plurality of liquid temperature sensors 50 are located soas to be adjacent to proximal balloon 26 when it is located in pneumaticchamber 40 and substantially filled with liquid 32 in order to produce asignal indicative of the temperature of the liquid in proximal balloon26. In the preferred embodiment heater temperature sensors 48 and liquidtemperature sensors 50 are T-type thermocouples. Pneumatic chamber 40 isconnected in an airtight manner to a pneumatic pressurizing means 52.

[0043] When the disposable component 4 is installed in reusablecomponent 2, locking connectors 54 located on the distal end ofpneumatic chamber 40 engage pneumatic fitting 24 such that rubber O-ring38 is compressed between pneumatic fitting 24 and pneumatic chamber 40providing an air tight seal. A disposable component detection means 55is located on pneumatic chamber 40 and adjacent to locking connectors 54which generates a signal when pneumatic fitting 24 is engaged on thedistal end of pneumatic chamber 40. In the preferred embodimentdisposable component detection means 55 is a mechanical contact switchhaving an actuator which generates an electrical signal when theactuator is depressed through contact with pneumatic fitting 24.Alternately, disposable component detection means 55 can be anelectrical contact mechanism and may further include an electrical fusearrangement in disposable component 4 in which the fuse is blown byapplying an electrical current from reusable component 2 after theapparatus is used to treat a patient. This allows detection of cases inwhich the user installs a previously used disposable component 4 inwhich case the apparatus could be configured to inhibit furtheroperation.

[0044]FIG. 4 shows a detailed cross section of the proximal end ofdisposable component 4 assembled within and reusable component 2. Wheninstalled in this manner, proximal balloon 26 is sealed within pneumaticchamber 40 in an air-tight manner. By modulating the pressure inpneumatic chamber 40 using pneumatic pressurizing means 52 the apparatusinitiates flow of liquid 32 between proximal balloon 26 and distalballoon 14 through catheter 16 and liquid ports 30. For example, if avacuum of −100 mmHg is maintained in pneumatic chamber 40 relative toambient pressure, liquid 32 will be drawn from distal balloon 14 suchthat after a short period of time, substantially all of liquid 32 willbe located in proximal balloon 26. Also for example, if a positivepressure of 180 mmHg is maintained in pneumatic chamber 40 relative toambient pressure, liquid 32 will tend to flow from proximal balloon 26into distal balloon 14. In this case, and when distal balloon 14 islocated within an enclosed cavity such as the uterus of a patient, andwhen this enclosed cavity is less than 30 ml in volume, after a shortperiod of time distal balloon 14 will reach a steady state in which avolume of liquid 32 is located in distal balloon 14 with a liquidpressure of 180 mmHg relative to ambient pressure.

[0045]FIG. 5 provides details of the preferred embodiment of pneumaticpressurizing means 52. In the preferred embodiment, pneumaticpressurizing means 52 comprises a solenoid activated 2-way, 2-positionvalve 56, a solenoid activated 4-way, 2-position valve 58, a pneumaticpressure transducer 60, a pneumatic pump 62 and flexible pneumatictubing 64. The configuration shown in FIG. 5 allows pneumaticpressurizing means 52 to generate either positive or negative pneumaticpressure at an input port of 2-way, 2-position valve 56 by switching4-way, 2-position valve 58 and operating pneumatic pump 62. The 2-way,2-position valve 56 is switched to either connect pneumatic chamber 40to this input port or alternately to connect pneumatic chamber 40directly to atmosphere for rapid venting of air within pneumatic chamber40. Pressure transducer 60 provides an output signal indicative of thepressure within pneumatic chamber 40 relative to ambient pressure andmust be capable of measuring both positive and negative pressures.Pneumatic pump 62 is capable of start-up and operating over a range ofpressures of at least −100 mmHg to +180 mmHg relative to ambientpressure. It will be understood by one skilled in the art that a varietyof apparatus could be similarly utilized in order to act as pneumaticpressurizing means 52.

[0046]FIG. 6 shows details of the control system contained withinreusable component 2. Re-usable component further comprises amicrocontroller 66 with an integral timer 68, and an electrical powersupply 70. In the preferred embodiment, display means 10 is an LCDmodule and user controls 12 comprise an on/off power switch 72 and aninflate switch 74. Microcontroller 66 accepts as inputs signals fromheater temperature sensors 48, liquid temperature sensors 50, disposablecomponent detection means 55, pressure transducer 60, and inflate switch74. Microcontroller 66 has outputs which control operation of heatingelement 42, pneumatic pressurizing means 52 and display means 10. On/offpower switch 72 provides a means for an operator to connect ordisconnect microcontroller 66 and thereby all electrical components ofthe invention from electrical power supply 70 and thereby initiate orterminate operation of the apparatus.

[0047] In the preferred embodiment, microcontroller 66 operates tocontrol operation of the system to allow a user to deliver thermalballoon ablation treatment to the uterine cavity of a patient. The userfirst activates the device by turning on-off power switch 72 to the “on”position. This provides power to microcontroller 66 which in turnprovides power as required to all electrical components of the inventionand initiates the software program which is resident in microcontroller66.

[0048] Microcontroller 66 first acts to poll disposable componentdetection means 55 to determine if a disposable component 4 has beenproperly inserted and locked into reusable component 2. If no disposablecomponent 4 is detected, microcontroller issues a notice to the user viadisplay means 10 and continues to poll disposable component detectionmeans 55. When a disposable component 4 is detected, operation ofmicrocontroller 66 proceeds to pre-heat liquid 32.

[0049] Pre-heating liquid 32 involves the following steps. Firstpneumatic pressurizing means 52 is activated to draw and maintain apneumatic pressure of approximately −100 mmHg relative to atmosphere inpneumatic chamber 40. This has the effect of drawing substantially allof liquid 32 into proximal balloon 26 which is sealed inside pneumaticchamber 40. Then, after a period of approximately 30 seconds,microcontroller activates heating element 42 and monitors the signalsfrom heater temperature sensors 48 and liquid temperature sensors 50. Apressure of approximately −100 mmHg is maintained in pneumatic chamber40 throughout the pre-heating of liquid 32. In the event that thetemperature of heating element 42 exceeds 200C as indicated by heatertemperature sensors 48, microcontroller turns heating element 42 offuntil the measured heater temperature drops below 165C. This is toprevent excessive temperatures at the surface of heating element 42 fromdamaging proximal balloon 26. Pre-heating of the liquid is terminatedwhen liquid temperature sensors 50 indicate that liquid 32 withinproximal balloon 26 reaches a temperature of 165C. In practice,pre-heating of liquid 32 typically requires about 5 minutes. During thispre-heating period, microcontroller 66 implements test routines in orderto detect leaks or problems with the apparatus and proceeds to generatewarnings to the user via user display 10 or inhibit further operation aswarranted. These are not described but will be apparent to those skilledin the art. When pre-heating is terminated, the invention is ready foruse to treat a patient.

[0050] When the invention is ready for use to treat a patient,microcontroller 66 outputs a suitable message via display means 10.Microcontroller 66 then operates pneumatic pressurizing means 52 tomaintain a pressure of approximately −100 mmHg in pneumatic chamber 40and operates to maintain liquid 32 within proximal balloon 26 at atemperature between 160C and 170C. Maintaining the temperature of liquid32 in this range is achieved by cycling heating element 42 on and off inresponse to signals from heater temperature sensors 48 and liquidtemperature sensors 50 in a similar manner to that described duringpre-heating of liquid 32. When the invention is ready to treat apatient, microcontroller 66 also monitors inflate switch 74 to determinewhen it is activated by the user.

[0051] When the invention is ready for use to treat a patient, the userinserts the distal end of disposable component 4 through the cervicalopening of the patient until flange 20 rests against the cervixpreventing further insertion. This operation precisely locates thedistal balloon 14 and distal sheath 18 in the uterine cavity as requiredfor treatment. It is expected that the patient has been prepared forsurgery and may have received a sedative or anesthetic. It is alsoexpected that the user will have confirmed that the depth and volume ofthe uterine cavity are suitable for use of the described invention.After the distal balloon 14 and associated components have been properlylocated in the patient, the user activates inflate switch 74 to begintreatment.

[0052] When microcontroller 66 detects activation of inflate switch 74,it proceeds to implement a treatment cycle as follows. First heatingelement 42 is turned off. Next, timer 68 is activated and pneumaticpressurizing means 52 releases the −100 mmHg vacuum in pneumatic chamber40 to atmosphere through 2-way, 2-position valve 56. Pneumaticpressurizing means 52 is then activated to generate and maintain apneumatic pressure of 180 mmHg in pneumatic chamber 40. This has theimmediate effect of forcing 165C liquid 32 from the proximal balloon 26through catheter 16 and liquid ports 30 into distal balloon 14 which islocated in the uterus of the patient. After a short period of time, theliquid in distal balloon 14 reaches a steady state pressure of 180 mmHg.At this pressure, the uterus will be fully distended and distal balloon14 will be filled with heated liquid 32 and be in contact withsubstantially all of the walls of the uterine cavity. In this steadystate, the liquid pressure inside distal balloon 14 will be essentiallyequal to the liquid pressure inside proximal balloon 26 and thepneumatic pressure inside pneumatic chamber 40. The microcontrolleroperates to automatically maintain this pressure in pneumatic chamber40, and thereby distal balloon 14 for a period of 90 seconds asindicated by timer 68. During this 90 second period thermal energy fromheated liquid 32 within distal balloon 14 is dissipated to thesurrounding tissue of the uterus and results in the desiredcauterization of the endometrial tissue. During this 90 second period,the temperature of liquid 32 in distal balloon 14 will decrease as theheat energy is dissipated to the surrounding tissues. The nature of thiscooling will be dependent of the specific anatomy of the uterine cavityundergoing treatment. In some cases in order to minimize this coolingeffect it may be advantageous for microcontroller 66 to pulse thepneumatic pressure in pneumatic chamber 40 during the treatment periodin order initiate flow back and forth between distal balloon 144 andproximal balloon 26 to continually mix the volume of heated liquid 32contained within disposable component 4.

[0053] When the 90-second treatment period is completed, microcontroller66 proceeds to control operation of the invention as follows. First,timer 68 is reset and pneumatic pressurizing means 52 releases the 180mmHg pressure in pneumatic chamber 40 to atmosphere through 2-way, 2position valve 56. Pneumatic pressurizing means 52 is then activated togenerate and maintain a pneumatic pressure of approximately −100 mmHg inpneumatic chamber 40. This has the immediate effect of withdrawingliquid 32 from distal balloon 14 back into proximal balloon 26 throughcatheter 16 and liquid ports 30. After 15 seconds as indicated by timer68, microcontroller 66 generates a message to the user via display means10 indicating that distal balloon 14 has been deflated and can beremoved from the uterus of the patient. It is expected that the userwill then remove the apparatus from the patient.

[0054] After another 120 seconds as indicated by timer 68,microcontroller 66 operates to vent pneumatic chamber 40 to atmospherethrough 2-way, 2-position valve 56 and generates a message to the uservia display means 10 indicating that the user can remove and discarddisposable component 4. Microcontroller 66 then monitors disposablecomponent detection means 55 in order to detect when disposablecomponent 4 is removed from reusable component 2 for discard. Whenremoval is detected microcontroller 66 continues to poll forinstallation of a new disposable component 4 in order to allow anotherpatient to be treated or the invention can be turned off by the userusing on/off power switch 72.

[0055] The described operation of the invention is for illustrationpurposes only. It will be obvious to one skilled in art that there arenumerous possible modifications to the operation of the invention asdescribed.

[0056]FIG. 7a Shows deployment of the distal end of disposable component4 during treatment of a 7 cm deep uterus which is the smallest indicateduterus for use of the preferred embodiment of the invention. FIG. 7bshows deployment of the distal end of disposable component 4 duringtreatment of a 12 cm deep uterus which is the largest indicated uterusfor use of the preferred embodiment of the invention. The outlines ofdistal balloon 14 prior to inflation 76 and after inflation 78 withliquid 32 to a pressure of 180 mmHg. This shows how the inventionoperates to treat the indicated range of uterine sizes after insertingdisposable component 4 through the cervical canal until flange 20prevents further insertion. When the user properly operates the deviceby inserting disposable component 4 through the cervical opening andinto the uterus of a patient in this manner, the invention does notrequire a user to adjust insertion depth based on uterine length,minimizing the risk of perforating the uterus, and providing thermalprotection of the cervical canal by ensuring distal sheath 18 and theunderlying thermal insulating material 36 are properly located betweenthe internal os and external os of the cervix.

[0057]FIG. 8 shows an alternate embodiment of the device. In thisalternate embodiment, heating element 42, and one or more of liquidtemperature sensors 50 are located within distal balloon 14. Thisembodiment further includes a multi-conductor electrical cable 80 and anelectrical connector 82 which operates to make electrical contact whenpneumatic fitting 24 is engaged by locking connectors 54.Multi-conductor electrical cable 80 and electrical connector 82 functionin order to provide power from electrical power supply 70 to heatingelement 42 and to control operation of said heating element 42 viaoperation of microcontroller 66. Multi-conductor electrical cable 80 andelectrical connector 82 also function to convey signals from liquidtemperature sensors 50 indicative of the liquid temperature withindistal balloon 14 to microcontroller 66. In the alternate embodiment,heating element 42 is a liquid-tight, 40W, electrical resistance typeheater and liquid temperature sensors 50 are T-type thermocouples.

[0058] Operation of the alternate embodiment differs from the preferredembodiment in that liquid 32 is not heated prior to initiation oftreatment, but is instead heated after distal balloon 14 is insertedthrough the cervical opening into the uterus and inflated to a pressureof 180 mmHg by pneumatic pressurization of pneumatic chamber 40. Whenthe user initiates treatment by pressing inflate switch 74,microcontroller 66 operates to inflate distal balloon 14 as described inthe preferred embodiment then operates control heating element 42 toheat the liquid within the distal balloon to a pre-determinedtemperature as indicated by liquid temperature sensors 50. In thealternate embodiment microcontroller 66 maintains said liquidtemperature for a predetermined time as measured by timer 68 beforewithdrawing the liquid into the proximal balloon 26 by operatingpneumatic pressurizing means 52 to draw a negative pressure in pneumaticchamber 40. In this alternate embodiment it is desirable that liquid 32be of a viscosity such that it readily flows through catheter 16 andliquid ports 30 for inflation of distal balloon 14. For example, salinesolution can be used as liquid 32, in which case heating of the liquidis restricted to temperatures substantially below 100C to preventboiling. In the alternate embodiment and using saline solution as liquid32 a liquid temperature of approximately 85C and a treatment time ofapproximately 10 minutes have been found effective to cauterize theendometrium. Use of other liquids with low viscosity and higher boilingpoints, such as perfluoroperhydrophenanthrene (C14F24) allows use ofhigher treatment temperatures and shorter treatment times.

[0059] It will be appreciated by one skilled in the art that a varietyof alternate embodiments exist for the disclosed inventions which mayalso specifically include a combination of the two described embodimentssuch that heating of liquid 32 is initiated by heating elements locatedin both reusable component 2 and disposable component 4. Specificallythis combination would be advantageous where it is desired to locateheating element 42 in distal balloon 14, however, liquid 32 is highlyviscous and must be heated above ambient temperature by a heatingelement external to distal balloon 14 in order to adequately flowthrough catheter 16 and liquid ports 30 for inflation of distal balloon14. For example, this allows use of 100% Glycerin as the liquid 32,which is highly viscous at room temperature but can be heated totemperatures of over 165C without boiling.

[0060] It will also be recognized that the described apparatus couldreadily be modified by replacing heating element 42 with a cooling meansin order to enable injection of cold liquid into distal balloon 14 tocauterize the endometrium. Similarly it will be understood by oneskilled in the art that the disclosed apparatus could readily bemodified to effect thermal balloon ablation of other cavities or ductsin the human body, such as the urethra for treatment of pathologicalconditions of the prostate gland.

[0061] It will be apparent from the foregoing that, while particularforms of the invention have been illustrated and described, variousmodifications can be made without departing from the spirit or scope ofthe invention. Accordingly, it is not intended that the invention belimited except as by the appended claims.

1. A device for causing necrosis of tissue comprising: a liquid-tight system having a distal flexible member; a proximal flexible member; and a catheter joining and providing a liquid path between said distal and proximal members, the system containing a liquid; a pneumatic chamber into which the flexible proximal member may be inserted; a means to controllably heat the contents of the pneumatic chamber and thereby heat the liquid in the flexible proximal member; and a means to apply variable pneumatic pressure to the pneumatic chamber to initiate liquid flow between the distal member and the proximal member.
 2. An apparatus according to claim 1 where said means to apply variable pneumatic pressure includes a pneumatic pump, a pneumatic valve and a pressure transducer.
 3. An apparatus according to claim 1 where the means to controllably heat the contents of the pneumatic chamber comprises an electrically controllable heater and a plurality of temperature sensors.
 4. An apparatus according to claim 3 where one or more of the temperature sensors are located adjacent to the proximal member when said proximal member is sealed inside the pneumatic chamber such that said temperature sensors generate an output signal indicative of the temperature of the liquid within the proximal member.
 5. An apparatus according to claim 1 where said controlling means further operates the apparatus to: (a) first draw substantially all of the liquid into the proximal member by applying and maintaining a negative pressure in the pneumatic chamber such that the distal member contains minimal liquid; (b) while maintaining this negative pressure in the pneumatic chamber, operate the means to heat the contents of the pneumatic chamber in order to heat the liquid within the proximal member to a pre-determined temperature; (c) then inject a volume of the heated liquid into the distal member by applying a positive pneumatic pressure to the pneumatic chamber; (d) then modulate the pressure in the pneumatic chamber such that the heated liquid is held in the distal member at a pre-determined pressure for a predetermined time; and (e) after said predetermined time withdraw the liquid from the distal member into the proximal member by applying a negative pressure to the pneumatic chamber.
 6. An apparatus according to claim 1 wherein the liquid within the liquid tight system is such that it can be heated to temperatures in excess of 100 degrees Celsius at sea level without boiling.
 7. An apparatus according to claim 1 where said catheter joining and providing a liquid path between said distal and proximal members includes a surrounding sheath of thermal insulating material covering a portion of the catheter where the sheath has a proximal and distal section which are separated by a flange of sufficient diameter such that it cannot be inserted through the cervical opening.
 8. A device for facilitating necrosis of tissue comprising: a distal flexible bladder; a proximal flexible bladder; a catheter joining said distal and proximal flexible bladders in a liquid tight system, a liquid inside the system to flow between the two bladders; wherein the liquid is in amount that permits the distal member to substantially deflate when the liquid is moved out of the distal end; and a connector for connecting the device to a pressurizing source.
 9. The device according to claim 8 further comprising a shield member for surrounding the proximal bladder and defining part of a pneumatic chamber in which the proximal bladder may be inflated and deflated thereby to cause liquid to flow between the two bladders.
 10. The device of claim 8 further comprising a heater member connectable to the connector for conveying heat to at least one of the distal and proximal bladders.
 11. A device according to claim 8 further comprising a chamber into which fits the proximal bladder, the chamber being in fluid communication with a pressurizing source for selectively increasing and decreasing the pressure in the chamber.
 12. The device of claim 8 wherein the liquid is of a type wherein the liquid viscosity substantially decreases when heated.
 13. A device according to claim 12 which further includes a means to heat the contents of the pneumatic chamber in order to reduce the viscosity of the liquid.
 14. A device according to claim 8 wherein the liquid within the liquid tight system is such that it can be heated to temperatures in excess of 100 degrees Celsius at sea level without boiling.
 15. A method for causing necrosis of a the tissue in a body cavity comprising the steps of: inserting a first bladder into a body cavity where said first bladder is in liquid communication with a second liquid filled bladder and preheating the liquid contained in said second bladder to a known temperature; forcing the heated liquid contained within said second bladder into said first bladder contained in the body cavity; maintaining the heated liquid in said first bladder for a predetermined time to dissipate heat energy to the tissues of the surrounding body cavity; and after said predetermined time, drawing the liquid contained in said first bladder back into said second bladder, thereby allowing removal of said first bladder from the body cavity.
 16. A method as described in claim 15 in which step (d) further includes heating the liquid contained in the first bladder using a heat releasing element located in the first bladder. 